On Sunday 04 January 2009, Jon Elson wrote:
>Gene Heskett wrote:
>> Interesting. The length of the radial portion of the bearing must be
>> fairly short then?
>
>The radial bearing sections are about 3/4" long, I think. These are
>combo hydrostatic/hydrodynamic bearings.
>I once had a hose blow off while drilling a hole, and waited until the
>drill was out of the hole to pause EMC and shut off the motor.
>It seemed to spin down pretty normally without the bearing air.
>
I'd have assumed the 'hydrodynamic' would have held it properly even without
pressure at that rpms, allowing contact and drag only when it had slowed
considerably.
[...]
>> How fast could it be brought to
>> speed?
>
>It can be accelerated quite quickly. As my VFD was never intended to
>run a motor like this, I take it easy on the startup and slowdown, and
>the VFD becomes noticeably warm when I run it. It stays stone cold when
>running my 1 Hp Bridgeport. I think I have it set to accelerate to
>24,000 RPM in 1.5 seconds.
>
I wonder if a triplet of stepdown transformers would more properly match the
vfd's current abilities to that particular motors requirements? A 2/1 ratio
might be worth a try just for grins. That might require a minimum speed
setting to prevent core saturation in the iron though, as allowing that would
be pretty hard on the vfd. With typical iron from Herbach & Rademan, not
less than 50 hz for a low limit should prevent that.
>Jon
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
First Law of Socio-Genetics:
Celibacy is not hereditary.
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